Improvement in safety-valves for steam-boilers



'UNITED STATES PATENT EEICE.

ALEXANDER M. JOHNSTON AND SAMUEL GlSSINGER, OF PITTSBURG, PA.

IMPROVEMENT IN SAFETY-VALVES FOR STEAM-BOILERS.

Specification forming part of Letters Patent No. 159,580, datedFebruary 9, 1875; application led August 17, 1874.

To all whom it may concern:

Beit known that we, ALEXANDER M. JOHN- sToN and SAMUEL GIssINGEE, of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Satety-Valve for Steam-Boilers 5 and we do hereby declare that the following is a full and exact description thereof, refer ence being had to the accompanying drawings and to the letters of reference marked thereon.

Our invention relates to an improvement in safety-valve for steam-boilers; and consists in a blow-oit' dome, a double valve-seat, two valves, one operating within the other, the stems of said valves being pivoted to weighted levers, the valve having the smallest diameter being used for the purpose of allowing the steam to escape from the boiler when slightly above the required pressure, and the larger valve `being` used for the purpose of relievin g the boiler from undue pressure, caused by a sudden increased pressure ot' steam, or steam and gases combined.

' To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation.l

In the accompanying drawings, which form part oi' my specification, Figure- 1 is a side elevation ot' my improvement in safety-valve for steam-engines. Fig. 2 is a vertical section of the same. Fig. 3 is a perspective view of the valves with their ports in an open position.

Referring to Vthe drawing, A represents a section of a steam-boiler, surmounted by a steam-dome, C, and provided with the safetyvalves E and j, arranged in the interior of the dome. B is an opening extending from the steam-boiler into the valves. D represents the double valve-seat, having an opening, a', leading into the small valve j. The large valve E rests on the lower seat, fw, and its stem f, which is provided with openings, as shown in Fig. 3, surrounds the small valve j and its stem la, the stem f of the valve E being pivoted, at g, to the weighted lever h, and the stem 7c of the small valve'j being pivoted,

at l, in the weighted lever m, as shown in Figs. l and 2. The weighted levers h and m are pivoted to the standard o, as shown at t' and n, and provided with suitable weights r and s, respectively. The lever h is also provided with a guide, p.

In the operation of the above-described parts, the small valve j is used for the purpose used for the purpose of relieving the boiler from undue pressure, when caused by a suddenlyincreased pressure of steam, or steam and gases combined, and when the small valve j would be inadequate for the purpose.

Between the valve-seat w and the double valve-seat D are arranged. a series of openings, as shown in Fig. 3, the object of which is such that, when the small valve 7' would fail to discharge the overplus of steam, the force of the same would also lift the larger valve E, and the steam would be discharged through these openings into the steam-dome O, and from thence through the opening u in the side of the same.

Having thus described our improvement, what we claim as ot' our invention is- 'lhe combination of the double seatD, valves E and j, levers h m, weights r and s, standard o, and dome O, constructed, arranged, and operating, with relation to each other substantially as herein described, and for the purpose set forth.

ALEXANDER M. JOHNSTON. S. GISSINGER. Witnesses:

A. G. JoENsToN, PARKER H. SWEET, Jr. 

